Escaping the Mist Ninja starts with backstabbing your teacher.

The combination of the Mist Ninja, the Kaguya clan, and the Shikotsumyaku (Corpse Bone Pulse) meant their fate was sealed – certain annihilation. Therefore, he decided to flee the Mist Ninja before the Third Shinobi World War ended, intending to betray his teacher, seize the Byakugan, and escape.